Mycobacterium tuberculosis (Mtb) is a widespread pathogenic bacterial species that causes tuberculosis, one of the most deadly diseases, killing over one million people each year and infecting one third of the world's population. Early diagnosis is critical to the prevention and control of tuberculosis due to its airborne transmission. Standard diagnostic methods, acid-fast smear from sputum, do not become positive until after transmission can occur, allowing spread of disease. Culture-based techniques are more sensitive, but take weeks to obtain results, due to the extremely slow growth rate of Mtb. Tuberculosis research and clinical diagnosis would be greatly facilitated by methods that can detect tubercle bacilli in a sensitive, rapid, specific and quantitative manner in vitro and during disease.
Tubercle bacilli naturally express beta-lactamase (BlaC), an enzyme that belongs to the class A β-lactamase family. Extended spectrum class A β-lactamases are capable of hydrolyzing all classes of β-lactam substrates, including cephalosporins. The mechanism of cephalosporin hydrolysis by β-lactamases yields hydrolyzed β-lactam, and more importantly, may be concomitant with the loss of the 3′ leaving group, depending on the group. Based on this mechanism, a number of fluorogenic and bioluminogenic probes have been developed for detection of β-lactamase activity in vitro, in living cells, and even in whole animals.
Current probes lack specificity for BlaC in Mtb; the common TEM-1 β-lactamase (TEM-1 Bla) in gram-negative bacteria can also generate fluorescence with these probes, which would reduce their accuracy for use in tuberculosis diagnosis. These probes are generally large and display slow hydrolytic kinetics for BlaC.
Despite the advances in the development of fluorescent probes for the detection of beta-lactamase and the diagnosis of tuberculosis, a need exists for novel probes that facilitate the rapid detection of tuberculosis. The present invention seeks to fulfill this need and provides further related advantages.